Sunday, May 1, 2011

Can You 'Catch' Obesity From A Common Cold?

In the never-ending cycle of hyper-inflated science "breakthrough" claims making their rounds in the news of late, one in particular is generating a lot of discussion: the idea that obesity may be caused by a common cold virus. But before you press the panic button because your child has the sniffles, you should know a little bit beyond the sound bites.

A study published online September 20, 2010 in the journal Pediatrics found that children who had been exposed to adenovirus-36 were more likely to be obese than children who had not. It found that whereas 7% of normal-weight kids had such antibodies, 22% of obese children did. What's more, it discovered that kids with evidence of previous adenovirus-36 infections were about 35 pounds heavier on average than obese children who hadn't caught the virus.

The study adds to several others, including one of Korean children and one of American and Italian adults, which have turned up higher rates of the virus in those who are obese. About 30% of obese adults carry antibodies x against adenovirus 36, compared to 10% of normal weight people. And there is lab research to back it up. Chickens, mice, rats, and monkeys infected with the virus show weight gain, even when they don't eat more or exercise less. Experiments with human cells grown in laboratory dishes also provide a potential mechanism for such a correlation: adult stem cells infected with the virus make more fat cells, and those fat cells store more fat than normal cells.

These are intriguing correlations to be sure, but before you start believing that obesity is caused by a virus, we need to put these findings through a little bit of a reality check, in order to place this knowledge in its proper perspective.

Why Obesity Can't be Blamed On A Virus
It's important to note that the vast majority of obese kids in the study DID NOT have antibodies for the virus (78%), which means that most kids are getting fat for reasons other than a cold virus. Even if such a cause and effect does exist, it is but a small player in the child obesity epidemic. When you further consider that 7% of kids tested positive for the virus yet were maintaining a normal weight, this would seem to indicate that catching the virus hardly dooms a child to obesity, and that it DOES NOT trump environmental factors. (85% of kids have already demonstrated the virus to be irrelevant, so only 15% of the issue is even up for debate.)

There are other reasons to be cautious. The sample size was relatively small, consisting of just 67 obese and 57 normal-weight children. If I flip a coin 124 times, I may very well end up with a differential of plus or minus 15 for either heads or tales, but that doesn't necessarily mean the results are anything more than random. Since obese kids have weaker immune systems and get sick more often, this finding could be corollary and not causative. Considering that two other studies have failed to provide a link between adenovirus-36 and obesity, this link, while interesting and worth exploring, is still far from established fact.

Even Jeffrey Schwimmer, a pediatric gastroenterologist at the University of California, Sand Diego and author of the study admits that a link between the virus and obesity doesn't mean the virus causes weight gain: "I don't think we know enough to say, 'Oh, if you get this virus you're going to be obese,'" he told Science News.

So while it's an interesting development that is being further explored, this does not mean that children catch obesity from a virus. The good news is that a vaccine against the virus is already in existence, so if this link does become established, we can easily address the problem.

One last note: you can't "catch" this virus from obese people, as some rumors have already begun to allege. So let's not go getting all silly with prejudice. The virus is long gone before any obesity-related effects would take place.

In the mean time, the tried and proven method for preventing childhood obesity is just as true as ever, and will remain so far into the future, regardless of what happens on this topic: proper diet, filled with fruits and vegetables, combined with plenty of exercise, will always overcome any genetic or viral influence.

1. Tina Hesman Saey, "Exposure to cold virus linked to obesity epidemic among children." Science News, 178(8):5-6, Oct. 9, 2010

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